Substrate for electronic device and electronic device

ABSTRACT

A substrate includes a plurality of through electrodes. The through electrode has a nanocomposite structure including a nm-sized carbon nanotube and is a casting formed by using a via formed in the substrate as a mold.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate for an electronic deviceand an electronic device.

2. Description of the Related Art

In electronic devices such as various scales of integrated circuits,various types of semiconductor elements and chips thereof, for example,there has been employed a method of disposing an element on a substrateand connecting them by means of wire bonding or the like. However, thismethod not only requires the process of wire bonding but also increasesthe mounting area with the number of elements, so that the signal delayincreases because of an increase in wiring length.

Therefore, there has been proposed a TSV (through-silicon-via)technology of providing a substrate with through-electrodes andreplacing the conventional wire bonding with the through-electrodes.Japanese Unexamined Patent Application Publication Nos. 11-298138,2000-228410, 2002-158191 and 2003-257891 disclose a through electrodeformation technology essential for the TSV technology. The superiorityof the TSV technology over the wire bonding is as follows.

At first, the number of connections is limited to 100 to 200 in the wirebonding, but the use of the TSV technology makes it possible to arrangeconnecting through electrodes at intervals of the order of μm,increasing the number of connections to several thousand.

In addition, there can be obtained advantages as follows: sinceconnection distance can be minimized, it is less likely to be affectedby noise; since parasitic capacitance and resistance are low, it ispossible to reduce delay, attenuation, or waveform degradation; anadditional circuit is not required for amplification or electrostaticbreakdown protection; and with these advantages, there can be realizedhigh speed action and low power consumption of the circuit.

The use of the TSV technology makes it possible to obtain not only anelectronic device including an analog or digital circuit, a memorycircuit such as a DRAM, a logic circuit such as a CPU or the like butalso an electronic device including different types of circuits such asan analog high frequency circuit and a low frequency, low powerconsumption circuit prepared in different processes and stackedtogether.

By applying the TSV technology to a three-dimensional integrated circuit(3D-IC), many functions can be packed into a small footprint. Inaddition, important electrical pathways between elements can bedramatically shortened to increase processing speed.

In order to apply the TSV technology, a via (through electrode) must beformed. For this purpose, there has been widely used a method of forminga through electrode by Cu electroplating.

However, the electroplating decreases the production efficiency becauseof its inevitable long processing time. Moreover, since the viatypically has an aspect ratio of 5 or more and usually has a ruggedinner wall surface, it is difficult to uniformly form a plating primaryfilm over the inner wall surface of the via. This produces a void or gapbetween the inner wall surface of the via and a plating film to be usedas the through electrode, thereby causing an increase in electricalresistance, decreased reliability and so on. Furthermore, there is alsosuch a limit that the electrical resistance cannot be set lower than theinherent electrical resistance of Cu.

Still furthermore, the progress in improving the packaging density, theperformance and the processing speed and reducing the size, thethickness and the weight of the electronic device because of the use ofthe TSV technology not only increases heat that will be generated by theoperation but also makes it difficult to prepare a heat dissipationstructure for it, so that the question of how to dissipate heat becomesa major issue. If the heat dissipation is insufficient, accumulation ofthe generated heat leads to abnormal heat generation, impairing bondingstrength of the electronic component and damaging reliability of theelectrical connection or changing electrical characteristics of theelectronic component and at worst, causing thermal runaway, thermalbreakdown or the like.

As such a heat dissipation means, there have been known various types oftechnologies. For example, Japanese Unexamined Patent ApplicationPublication No. 2008-294253 discloses a technology of forming a heattransmission via conductor by filling a conductive paste including Agpowder. On the other hand, Japanese Unexamined Patent ApplicationPublication No. 2005-158957 discloses a technology of forming a thermalvia, wherein the thermal via comprises a metal (copper, solder or gold)having a good thermal conductivity and a via is formed from an uppersurface of a light-emitting element submount structure, the via iscoated with gold at its side face and then filled with solder. JapaneseUnexamined Patent Application Publication No. 10-098127 discloses athermal conductor comprising a metal powder-containing resin such as asilver paste or a copper paste, a composite of a metal rod and the metalpowder-containing resin or the like. Moreover, Japanese UnexaminedPatent Application Publication No. 2007-294834 discloses a thermal viacomprising a metal such as Cu or Ni. However, any related art has aproblem to be solved, such as improvement in heat dissipationcharacteristics, manufacturing cost reduction or the like.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a substrate for anelectronic device with a heat transfer pathway having excellent heatdissipation characteristics and an electronic device using the same.

It is another object of the present invention to provide a substrate foran electronic device with a through electrode structure having a lowelectrical resistance and an electronic device using the same.

It is still another object of the present invention to provide asubstrate for an electronic device in which a through electrodestructure having a low electrical resistance and a heat transfer pathwayhaving excellent heat dissipation characteristics can be formedefficiently in a short time and an electronic device using the same.

In order to achieve the above object, a substrate for an electronicdevice according to the present invention comprises a plurality ofthrough electrodes, the through electrode having a nanocompositestructure including a nm-sized carbon nanotube and being a castingformed by using a via formed in the substrate as a mold.

In the present invention, the term “nm-sized” means having a size withina range of 1 μm or less. On the other hand, the term “nanocompositestructure” means that at least two kinds of components are combined toconstitute a composite where the components are nm-sized particles or ina crystal or amorphous phase.

In the substrate according to the present invention, since the throughelectrode is a casting formed by using a via formed in the substrate asa mold, as described above, the substrate can be provided with a throughelectrode that has a high adhesion strength to a side wall surface ofthe via, a compact structure free from any cavity, void or hollow, a lowelectrical resistance and an excellent electrical conductivity. Even ifthe inner wall surface of the via has irregularities, the throughelectrode can be casted to conform to the irregularities, so that therecan be obtained a through electrode having a high adhesion strength tothe via.

Moreover, since the through electrode can be casted to conform to theirregularities of the inner wall surface of the via, the throughelectrode and the irregularities of the inner wall surface of the viaserve as an anchor for preventing slippage of the through electrode,thereby increasing the bonding strength of the through electrode to thesubstrate. This means that unlike in the case where the throughelectrode is formed by plating, the inner wall surface of the via doesnot require accuracy for the irregularities, but rather a preferableresult can be obtained with certain irregularities. This makes it easyto form the via.

Since there are two or more through electrodes, the through electrodescan be used as a positive or negative electrode for an electroniccomponent or an electronic device to be mounted on the substrate.Therefore, electrical wiring such as wire bonding becomes unnecessary,so that the product cost can be reduced by cutting the productionfacility cost that has been spent on an expensive wire bondingapparatus.

Furthermore, the through electrode has a nanocomposite structureincluding a nm-sized carbon nanotube. The carbon nanotube has a highthermal conductivity which is 10 times greater than that of copper. Thismakes it possible to realize a through electrode having extremely highheat dissipation characteristics.

The carbon nanotube also has a high current density resistance of 10⁹A/cm² which is more than 1,000 times greater than that of copper.Moreover, since the carbon nanotube has less electron scattering ascompared with copper being a good electrical conductor, it has a lowelectrical resistance. As compared with copper, accordingly, the throughelectrode including a carbon nanotube has a low electrical resistanceand can reduce the quantity of heat due to resistance even if a largecurrent is passed.

The through electrode has a nanocomposite structure including a nm-sizedcarbon nanotube having such characteristics. In the through electrodehaving a nanocomposite structure, stress can be reduced because of thenm-sized effect. This inhibits characteristic degradation of asemiconductor circuit in a semiconductor substrate. It can also inhibitthe occurrence of fracturing or cracking of the substrate.

The through electrode may comprise the carbon nanotube alone or may havea nanocomposite structure including the nm-sized carbon nanotube and ametal/alloy component having a nanocomposite crystal structure. Sincethe through electrode having a nanocomposite structure including thenm-sized carbon nanotube and the metal/alloy component having ananocomposite crystal structure includes a structure (crystal) whosesize is limited to a nano level, stress that will be generated in thethrough electrode can be reduced accordingly. Moreover, thenanocomposite crystal structure is also capable of facilitatingformation of equiaxed crystal in the vertical conductor. Theabove-described particular characteristics of the nanocomposite crystalstructure and the nanocomposite structure inhibit characteristicdegradation of a semiconductor circuit, particularly, in a semiconductorsubstrate. It can also inhibit the occurrence of fracturing or crackingof the substrate.

In the present invention, the term “nanocomposite crystal structure”basically refers to a structure in which nanoparticles are dispersed incrystal grains (intragranular nanocomposite crystal structure) or astructure in which nanoparticles are dispersed in grain boundaries(interglanular nanocomposite crystal structure).

It may also comprise a composite material that is turned into a paste bymixing the carbon nanotube with an organic material, wherein, ifnecessary, inorganic powder may be mixed or a metal/alloy componenthaving a nanocomposite crystal structure may be added as a thirdcomponent.

The substrate supporting the through electrode can include at least oneof an inorganic substrate such as of ceramic, an organic substrate suchas one used for a copper-clad substrate and a semiconductor substrate.In the case where the inorganic substrate and the organic substratecomprising the substrate have an electrical conductivity and in the casewhere it comprises the semiconductor substrate, the through electrode iselectrically insulated from the conductive inorganic substrate, theconductive organic substrate and the semiconductor substrate by anelectrical insulating film or layer. This insulating structure can berealized by an insulating film obtained by oxidizing or nitriding theinner wall surface of a via that will act as a mold for the throughelectrode or an insulating layer adhered to the inner wall surface ofthe via. The above-described insulating structure may be provided in theform of a ring at a small distance around the via.

According to another aspect, the present invention provides a substratecomprising a plurality of columnar heat sinks independently of or alongwith the through electrodes. The columnar heat sink is a casting formedby using a via formed in the substrate as a mold.

Since the columnar heat sink is also a casting formed by using a viaformed in the substrate as a mold, the substrate can be provided with acolumnar heat sink that has a high adhesion strength to the side wallsurface of the via, a compact structure free from any cavity, void orhollow and excellent thermal conductivity and heat dissipationcharacteristics.

Moreover, the columnar heat sink having a high adhesion strength to theside wall surface of the via and a compact structure free from anycavity, void or hollow can be formed efficiently in a short time, ascompared with the case where it is formed by using another method suchas plating.

The columnar heat sink has a nanocomposite structure including ametal/alloy component having a nanocomposite crystal structure. Thisresults in reducing stress that will be generated in the columnar heatsink. Moreover, the nanocomposite crystal structure is also capable offacilitating formation of equiaxed crystal in the columnar heat sink.

The above-described particular characteristics of the nanocompositecrystal structure and the nanocomposite structure inhibit characteristicdegradation of a semiconductor circuit formed on a semiconductorsubstrate (wafer). It can also inhibit the occurrence of fracturing orcracking of the semiconductor substrate.

The columnar heat sink may include a nm-sized carbon atom structurehaving an excellent thermal conductivity along with or independently ofthe metal/alloy component having a nanocomposite crystal structure. Sucha carbon atom structure includes at least one of a diamond, a fullereneand a carbon nanotube.

The above-described columnar heat sink has excellent heat dissipationcharacteristics because of the high thermal conductivity of the carbonatom structure. Particularly, the carbon nanotube has a high thermalconductivity which is 10 times greater than that of copper, ensuringextremely high heat dissipation characteristics. It may comprise acomposite material that is turned into a paste by further adding anorganic component as a third component, if necessary.

The substrate according to the present invention may comprise both thethrough electrode and the columnar heat sink. Specifically, it may beconstructed as follows.

(a) The through electrode has a nanocomposite structure including anm-sized carbon nanotube and is a casting formed by using a via formedin the substrate as a mold, while the columnar heat sink is a castingformed by using a via formed in the substrate as a mold.(b) In the above (a), the through electrode and the columnar heat sinkhave a nanocomposite structure including a metal/alloy component havinga nanocomposite crystal structure.(c) In the above (a), the columnar heat sink has a nanocompositestructure including a nm-sized carbon atom structure having an excellentthermal conductivity (a diamond, a fullerene, a carbon nanotube or thelike).(d) In the above (a), the columnar heat sink has a nanocompositestructure including a metal/alloy component having a nanocompositecrystal structure and a nm-sized carbon atom structure having anexcellent thermal conductivity.(e) The through electrode is a casting formed by using a via formed inthe substrate as a mold, while the columnar heat sink has ananocomposite structure including a metal/alloy component having ananocomposite crystal structure and is a casting formed by using a viaformed in the substrate as a mold.(f) In the above (e), the columnar heat sink has a nanocompositestructure including a nm-sized carbon atom structure.(g) The through electrode is a casting formed by using a via formed inthe substrate as a mold, while the columnar heat sink has ananocomposite structure including a nm-sized carbon atom structurehaving an excellent thermal conductivity (a diamond, a fullerene, acarbon nanotube or the like).

The above-described substrate can be combined with an electroniccomponent to provide an electronic device. In this case, the electroniccomponent is mounted on the substrate. Thus, an electrical circuit canbe made for the electronic component using the through electrode havinga low electrical resistance, while heat generated by the operation ofthe electronic component can be efficiently dissipated through thecolumnar heat sink, thereby avoiding characteristic change, malfunctionand even thermal runaway due to the heat generation of the electroniccomponent.

In the present invention, the electronic component may be an activeelement, a passive component or a composite element thereof. On theother hand, the electronic device may be almost any electrical productbased on the technology of the electronics. The electronic device mayalso be one having a three-dimensional multilayer structure based on theTSV technology or one having a three-dimensional multilayer structureconstructed by combining an interposer and various types of elements.

The present invention will be more fully understood from the detaileddescription given hereinbelow and the accompanying drawings which aregiven by way of illustration only, and thus not to be considered aslimiting the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing a part of a substrate according to thepresent invention;

FIG. 2 is a sectional view of the substrate shown in FIG. 1;

FIG. 3 is a SEM image of a section of a substrate according to thepresent invention;

FIG. 4 is a drawing showing a process of manufacturing a substrateaccording to the present invention;

FIG. 5 is a partial sectional view of an electronic device having asubstrate according to the present invention;

FIG. 6 is a drawing showing another embodiment of a substrate accordingto the present invention;

FIG. 7 is a partial sectional view of an electronic device having thesubstrate shown in FIG. 6;

FIG. 8 is a drawing showing another embodiment of a substrate accordingto the present invention;

FIG. 9 is a partial sectional view of an electronic device having thesubstrate shown in FIG. 8;

FIG. 10 is a partial sectional view showing one embodiment of alight-emitting device according to the present invention;

FIG. 11 is a plan view of a support used in the light-emitting deviceshown in FIG. 10;

FIG. 12 is a sectional view taken along line 12-12 in FIG. 11;

FIG. 13 is a drawing showing an appearance of a light-emitting elementused in the light-emitting device shown in FIG. 10;

FIG. 14 is a bottom view of the light-emitting element shown in FIG. 13;

FIG. 15 is a partial sectional view showing another embodiment of alight-emitting device according to the present invention;

FIG. 16 is a partial sectional view showing still another embodiment ofa light-emitting device according to the present invention;

FIG. 17 is a plan view of a lighting apparatus according to the presentinvention;

FIG. 18 is an enlarged sectional view showing a part of the lightingapparatus shown in FIG. 17;

FIG. 19 is a sectional view from which a light-emitting element and afluorescent body shown in the sectional view of FIG. 18 are removed;

FIG. 20 is a sectional view of light-emitting device according toanother embodiment;

FIG. 21 is a sectional view from which a light-emitting element and afluorescent body shown in the sectional view of FIG. 20 are removed;

FIG. 22 is a sectional view of a liquid crystal display according to thepresent invention;

FIG. 23 is a plan view of a pixel;

FIG. 24 is a plan view of a light-emitting diode display according tothe present invention;

FIG. 25 is a sectional view showing another embodiment of a substrateaccording to the present invention;

FIG. 26 is a partial sectional view of an electronic device having thesubstrate shown in FIG. 25;

FIG. 27 is a partial sectional view showing another embodiment of asubstrate according to the present invention;

FIG. 28 is a partial sectional view of an electronic device having thesubstrate shown in FIG. 27;

FIG. 29 is a partial sectional view showing another embodiment of anelectronic device according to the present invention;

FIG. 30 is a partial sectional view showing another embodiment of anelectronic device according to the present invention;

FIG. 31 is a partial sectional view showing another embodiment of anelectronic device according to the present invention;

FIG. 32 is a partial sectional view showing another embodiment of anelectronic device according to the present invention;

FIG. 33 is a sectional view showing a part of a heat dissipationsubstrate according to the present invention;

FIG. 34 is a sectional view showing a part of another embodiment of aheat dissipation substrate according to the present invention;

FIG. 35 is a sectional view showing a part of another embodiment of aheat dissipation substrate according to the present invention;

FIG. 36 is a sectional view showing a part of another embodiment of aheat dissipation substrate according to the present invention;

FIG. 37 is a sectional view showing a part of another embodiment of aheat dissipation substrate according to the present invention;

FIG. 38 is a sectional view showing a part of another embodiment of aheat dissipation substrate according to the present invention;

FIG. 39 is a plan view showing a part of another embodiment of a heatdissipation substrate according to the present invention;

FIG. 40 is a sectional view of the heat dissipation substrate shown inFIG. 39;

FIG. 41 is a sectional view showing a part of another embodiment of aheat dissipation substrate according to the present invention;

FIG. 42 is a sectional view showing a part of another embodiment of aheat dissipation substrate according to the present invention;

FIG. 43 is a circuit diagram of a vehicle-mounted electronic device;

FIG. 44 is a partial sectional view showing a heat dissipation structureof the vehicle-mounted electronic device shown in FIG. 43;

FIG. 45 is a partial sectional view showing a heat dissipation structurethat can be employed for an electronic device such as a personalcomputer or a mobile phone; and

FIG. 46 is a partial sectional view showing a heat dissipation structurethat can be employed for an electronic device such as a personalcomputer or a mobile phone.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 2, a substrate 1 for an electronic deviceaccording to the present invention comprises a plurality of throughelectrodes 2 arranged at a given pitch of the order of μm. The viadiameter of the through electrode 2 is also of the order of μm. Thethrough electrode 2 has a nanocomposite structure including a nm-sizedcarbon nanotube and is a casting formed by using a via 20 formed in thesubstrate 1 as a mold.

Since the through electrode 2 is a casting formed by using the via 20formed in the substrate 1 as a mold, as described above, the substrate 1can be provided with a through electrode 2 that has a high adhesionstrength to a side wall surface of the via 20, a compact structure freefrom any cavity, void or hollow, a low electrical resistance and anexcellent electrical conductivity. Even if the inner wall surface of thevia 20 has irregularities, the through electrode 2 can be casted toconform to the irregularities, so that there can be obtained a throughelectrode 2 having a high adhesion strength to the via 20.

Moreover, since the through electrode 2 can be casted to conform to theirregularities of the inner wall surface of the via 20, the throughelectrode 2 and the irregularities of the inner wall surface of the via20 serve as an anchor for preventing slippage of the through electrode2, thereby increasing the bonding strength of the through electrode 2 tothe substrate 1. This means that unlike in the case where the throughelectrode 2 is formed by plating, the inner wall surface of the via 20does not require accuracy for the irregularities, but it is ratherpreferable to have certain irregularities. This makes it easy to formthe via 20.

Referring to FIG. 3 showing a SEM image, the through electrode 2 isfilled in the via 20 formed in the substrate 1 to have a compactstructure free from any cavity, void or hollow, wherein the throughelectrode 2 is kept in close contact with the side wall surface of thevia 20 even though the side wall surface of the via 20 hasirregularities.

The via 20 can be drilled by laser, chemical etching, plasma etching orthe like and its inner wall surface has irregularities due to the viadrilling process, but as shown in FIG. 3, even though the inner wallsurface of the via 20 has irregularities, the through electrode 2 isfilled to conform to the irregularities and brought into close contactwith the inner wall surface of the via 20 to have a compact structurefree from any cavity, void or hollow. Moreover, since the irregularitiesof the inner wall surface of the via 20 create a kind of anchoringeffect, the through electrode 2 can be reliably secured within the via20 without causing loosening or floating from the via 20. In otherwords, this means that as compared with a common technique using bothsputtering and plating for its formation, the via 20 can be formed withless attention to the flatness of the inner wall surface, but rather apreferable result can be obtained by forming the via 20 with certainroughness.

The through electrode 2 has a nanocomposite structure including anm-sized carbon nanotube. The carbon nanotube is a material in which asix-member carbon ring (graphene sheet) is formed into a single- ormulti-walled coaxial tube. Either a single-walled nanotube (SWNT) or amulti-walled nanotube (MWNT) can be used. More specifically, there canbe used a composite material in which nm-sized carbon nanotubes areoriented and added as a filler into an aluminum alloy.

The carbon nanotube has a high thermal conductivity which is 10 timesgreater than that of copper, providing extremely high heat dissipationcharacteristics. The carbon nanotube also has a high current densityresistance of 10⁹ A/cm² which is more than 1,000 times greater than thatof copper. Moreover, since the carbon nanotube has less electronscattering as compared with copper being a good electrical conductor, ithas a low electrical resistance. As compared with copper, accordingly,the through electrode 2 including a carbon nanotube has a low electricalresistance and can reduce the quantity of heat due to resistance even ifa large current is passed. The carbon nanotube has a diameter of a fewnm and is cut into a length of 500 nm or less, preferably, 200 to 300nm, for use in the present invention.

The through electrode 2 may comprise the carbon nanotube alone or acomposite material including the carbon nanotube and a metal/alloycomponent having a nanocomposite crystal structure.

Since the through electrode 2 having a nanocomposite structure includingthe nm-sized carbon nanotube and the metal/alloy component having ananocomposite crystal structure includes a structure (crystal) whosesize is limited to a nano level, stress that will be generated in thethrough electrode 2 can be reduced accordingly. Moreover, thenanocomposite crystal structure is also capable of facilitatingformation of equiaxed crystal in the vertical conductor. Theabove-described particular characteristics of the nanocompositestructure and the nanocomposite crystal structure inhibit characteristicdegradation of a semiconductor circuit, particularly, in a semiconductorsubstrate. It can also inhibit the occurrence of fracturing or crackingof the substrate 1.

Examples of the metal/alloy component having a nanocomposite crystalstructure include Bi, In, Sn and Cu. Particularly when Bi is contained,the through electrode 2 can be formed compactly inside the via 20without leaving any hollow or void because of volumetric expansioncharacteristics of Bi during the solidification. However, since thepresence of Bi tends to increase the electrical resistance, it ispreferred that Bi is used to such an extent as to meet a requiredelectrical resistance.

It may also comprise a composite material prepared by mixing thenm-sized carbon nanotube with an organic material, wherein, ifnecessary, inorganic powder of ceramic, glass or the like or ametal/alloy component having a nanocomposite crystal structure may beadded thereto.

The substrate 1 supporting the through electrode 2 can include at leastone of an inorganic substrate such as of ceramic, an organic substratesuch as one used for a copper-clad substrate and a semiconductorsubstrate. Any type of semiconductor substrate can be used withoutparticular limitation. There can be used not only an Si substrate(silicon substrate), an SiC substrate (silicon carbide substrate), a GaNsubstrate (gallium nitride substrate) and a ZnO substrate (zinc oxidesubstrate) but also an SOI substrate (silicon on insulator substrate) orthe like. In the case where the inorganic substrate and the organicsubstrate comprising the substrate 1 have an electrical conductivity andin the case where the substrate 1 comprises the semiconductor substrate,the through electrode 2 is electrically insulated from the conductiveinorganic substrate, the conductive organic substrate and thesemiconductor substrate by an electrical insulating film or layer. Thisinsulating structure can be realized by an insulating film obtained byoxidizing or nitriding the inner wall surface of the via 20 that willact as a mold for the through electrode 2 or an insulating layer adheredto the inner wall surface of the via 20. The above-described insulatinglayer may be provided in the form of a ring at a small distance aroundthe via 20.

To form the through electrode 2, at first, as shown in FIG. 4(A), asubstrate 1 having a number of small vias 20 previously formed to passthrough it in the thickness direction is put on a support S1. The via 20is closed at its lower side by the support S1. Alternatively, the via 20may be a non-through-hole.

Then, as shown in FIG. 4(B), the vias 20 formed in the substrate 1 areused as a mold and an electrode material 2 in the form of liquid, pasteor powder is poured into them. Then, as shown in FIG. 4(C), theelectrode material 2 poured into the vias 20 is solidified while beingsubjected to a mechanical force F1 such as a pressing pressure using apressing plate P1, an injection pressure or a rolling pressure. Thus, asshown in FIG. 4(D), the through electrode 2 can be formed as a castinghaving a compact structure free from any cavity, void or hollow and keptin close contact with the side wall surface of the via 20. It should benoted that the structure of the casting can be seen from the SEM imageof FIG. 3.

Preferably, the process of pouring the electrode material 2 into thevias 20 formed in the substrate 1 is performed inside a vacuum chamberunder a reduced pressure. This is because differential pressure fillingcan be performed by using this reduced pressure and a pressure to beapplied subsequently.

In the case where the electrode material 2 has a nanocomposite structureincluding a carbon nanotube and a metal/alloy component having ananocomposite crystal structure, a liquid composite material 2 preparedby mixing a molten metal of the metal/alloy component with the nm-sizedcarbon nanotube is poured into the vias 20, and the poured liquidcomposite material 2 is cooled and solidified while being subjected to apressing pressure using the pressing plate P1, an injection pressure ora rolling pressure.

In the case where the electrode material 2 is a paste material includinga carbon nanotube, an organic material and a solvent, on the other hand,it is hardened by heating while being subjected to a pressing pressureusing the pressing plate P1, an injection pressure or a rollingpressure. In the case where the electrode material 2 is a powdermaterial, it may be poured into the vias 20 in a molten state or put inthe vias 20 in a powder state and then melted by heating.

FIG. 5 shows an electronic device in which the substrate shown in FIGS.1 and 2 is used as an interposer. The substrate 1 is disposed as aninterposer between electronic devices 6, 6 such as a semiconductor chip.The electronic devices 6, 6 have electrodes connected to the throughelectrode 2 through junction films 4, 4, respectively.

Since there are two or more through electrodes 2, the two or moreseparate through electrodes 2 can be used as a positive or negativeelectrode for the electronic devices 6, 6 to be mounted on the substrate1. Therefore, electrical wiring such as wire bonding becomesunnecessary, so that the product cost can be reduced by cutting theproduction facility cost that has been spent on an expensive wirebonding apparatus.

The substrate 1 may comprise columnar heat sinks independently of oralong with the through electrodes 2. Referring first to FIG. 6, thesubstrate 1 has columnar heat sinks 3. The columnar heat sink 3 is acasting formed by using a via 30 formed in the substrate 1 as a mold.Many columnar heat sinks 3 passing through the substrate 1 in thethickness direction are arranged at a small distance from each other,for example, in the form of matrix. The columnar heat sinks 3 have firstends (lower ends) connected together through a heat dissipation layer 31provided on a back surface (second surface) of the substrate 1 andsecond ends (upper ends) led to a front surface of the substrate 1.Another heat dissipation layer may also be provided on the frontsurface. In the case where the inorganic substrate and the organicsubstrate comprising the substrate 1 have an electrical conductivity,the columnar heat sink 3 is electrically insulated from the conductiveinorganic substrate, the conductive organic substrate and thesemiconductor substrate by an electrical insulating film or layer. Thisinsulating structure can be realized by an insulating film obtained byoxidizing or nitriding the inner wall surface of the via 30 that willact as a mold or an insulating layer adhered to the inner wall surfaceof the via 30. The above-described insulating layer may be provided inthe form of a ring at a small distance around the via 30.

Since the columnar heat sink 3 is also a casting formed by using the via30 formed in the substrate 1 as a mold, the substrate 1 can be providedwith a columnar heat sink 3 that has a high adhesion strength to theside wall surface of the via 30, a compact structure free from anycavity, void or hollow and excellent thermal conductivity and heatdissipation characteristics.

Moreover, the columnar heat sink 3 having a high adhesion strength tothe side wall surface of the via and a compact structure free from anycavity, void or hollow can be formed efficiently in a short time, ascompared with the case where it is formed by using another method suchas plating.

If a thermal via is formed after plating of the side face of the via 30as a technique for formation of the columnar heat sink 3, the inner wallsurface of the via 30 has to be a smooth surface having extremely smallirregularities so as to form a continuous plating film, which will needa long time for the via formation process. Moreover, if the via 30 has ahigh aspect ratio, it becomes extremely difficult to form a platingprimary film as a continuous homogeneous film.

In the present invention in which the columnar heat sink 3 is a castingformed by using the via 30 formed in the substrate 1 as a mold, on theother hand, even if the inner wall surface (side wall surface) of thevia 30 has irregularities, the columnar heat sink 3 can be filled toconform to the irregularities in the course of casting. Therefore, theobtained columnar heat sink 3 has a compact structure free from anycavity, void or hollow and in close contact with the side wall surfaceof the via 30. This realizes a columnar heat sink 3 having an excellentthermal conductivity and heat dissipation characteristics.

Moreover, since the irregularities of the inner wall surface of the via30 create a kind of anchoring effect, the columnar heat sink 3 can bereliably secured within the via 30 without causing loosening or floatingfrom the via 30. In other words, this means that as compared with aconventional technique, the via 30 can be formed with less attention tothe flatness of the inner wall surface, but rather a preferable resultcan be obtained by forming the via 30 with certain roughness.

Since many columnar heat sinks 3 are distributed over the substrate 1with their first ends (lower ends) connected together through the heatdissipation layer 31 provided on the back surface (second surface) ofthe substrate 1, there is formed a three-dimensional heat dissipationpathway in which heat transferred from the columnar heat sinks 3 in thethickness direction of the substrate 1 can be dissipated while beingdispersed in a direction parallel to a plane perpendicular to thethickness direction. This improves heat dissipation characteristics.Heat generated by the operation of the electronic component or theelectronic device 6 can be dissipated to the outside of the substrate 1more efficiently by properly selecting the thermal resistance of thematerial constituting the columnar heat sinks 3 and the occupancy rateof the columnar heat sinks 3.

Basically, the heat dissipation characteristics of the columnar heatsinks 3 depend on the thermal conductivity (or thermal resistance) ofthe constituent material and the total occupancy rate of the columnarheat sinks 3 to a plane area of the substrate 1. For example, if alow-thermal resistance material is used for the columnar heat sink 3,the occupancy rate can be reduced, while if a high-thermal resistancematerial is used, the occupancy rate can be increased. That is, theoccupancy rate of the columnar heat sinks 3 can be determined inconsideration of the thermal conductivity of the constituent material.On the other hand, if there is a limit to the occupancy rate, materialshaving a suitable thermal conductivity can be selected in considerationof required heat dissipation characteristics.

The columnar heat sink 3 can have a nanocomposite structure including ametal/alloy component having a nanocomposite crystal structure. Thisresults in reducing stress that will be generated in the columnar heatsink 3. Moreover, since the nanocomposite crystal structure is alsocapable of facilitating formation of equiaxed crystal in the columnarheat sink 3, the stress can be further reduced.

The above-described particular characteristics of the nanocompositecrystal structure inhibit characteristic degradation of a semiconductorcircuit formed on the substrate 1. It can also inhibit the occurrence offracturing or cracking of the substrate 1.

Specific examples of the nanocomposite crystal structure materialconstituting the columnar heat sink 3 include, but not limited to, Al,Au, Cu, Ag and Sn. However, since it is desirable to reduce the thermalresistance of the columnar heat sink 3 as much as possible, thematerial, composition ratio and so on should be determined from such aviewpoint. In the illustrated embodiment, the columnar heat sink 3 is asolid column having a circular section, but it may have a polygonalsection.

The columnar heat sink 3 may include a nm-sized carbon atom structurehaving an excellent thermal conductivity along with or independently ofthe metal/alloy component having a nanocomposite crystal structure. Atleast one of a diamond, a fullerene and a carbon nanotube can be givenas a specific example of such a carbon atom structure.

The columnar heat sink 3 including the carbon atom structure hasexcellent heat dissipation characteristics because of the high thermalconductivity of the carbon atom structure. Particularly, the carbonnanotube has a high thermal conductivity which is 10 times greater thanthat of copper, ensuring extremely high heat dissipationcharacteristics. More specifically, there can be used a material inwhich carbon nanotubes are oriented and added as a filler into analuminum alloy. In combination with the carbon nanotubes, vapor-growncarbon fibers having a larger fiber thickness may also be used as afiller. This composite material has a thermal conductivity which is morethan 3 times greater than that of the aluminum alloy. For use, thecarbon nanotube is cut into a length of 500 nm or less, preferably, 200to 300 nm.

When used in an electronic device, the heat dissipation substrateaccording to the present invention is provided with a heat-generatingelectronic component and used to dissipate the heat to the outside. FIG.7 shows one embodiment of such an electronic device. On one surface ofthe substrate 1 shown in FIG. 6, a heat-generating electronic componentor electronic device 6 is mounted through a thermally conductive binderlayer 51. Preferably, a heat dissipation block is thermally coupled tothe heat dissipation 31. The electronic component or electronic device 6is, for example, an active element such as a semiconductor chip, apassive component such as a capacitor or an inductor or a compositeelement thereof. The electronic component or electronic device 6 mayhave a semiconductor element and a passive component in combination ormay be a memory element, a logic circuit element or an analog circuitelement. It may have a single layer structure or a multilayer structureof such elements.

It should be noted that the substrate 1 according to the presentinvention has the columnar heat sink 3 being a casting formed by usingthe via 30 as a mold, and the columnar heat sink 3 creates a heatdissipation pathway that is in close contact with the side wall surfaceof the via 30 and has a compact structure free from any cavity, void orhollow and excellent thermal conductivity and heat dissipationcharacteristics. When it is used in an electronic device, therefore,heat generated at the electronic component or electronic device 6 can beefficiently and reliably dissipated through the columnar heat sink 3having an excellent thermal conductivity and heat dissipationcharacteristics, thereby avoiding abnormal heat generation, thermalrunaway or malfunction of the electronic component or electronic device6.

Referring next to FIG. 8, the illustrated substrate 1 comprises both thethrough electrode 2 and the columnar heat sink 3. In this case, thethrough electrode 2 and the columnar heat sink 3 may be combined asfollows. Substrate 1 has a first side 1B and a second side 1A.

(a) The through electrode 2 has a nanocomposite structure including anm-sized carbon nanotube and is a casting formed by using the via 20formed in the substrate 1 as a mold, while the columnar heat sink 3 is acasting formed by using the via 30 formed in the substrate 1 as a mold.(b) In the above (a), the through electrode 2 and the columnar heat sink3 have a nanocomposite structure including a metal/alloy componenthaving a nanocomposite crystal structure.(c) In the above (a), the columnar heat sink 3 has a nanocompositestructure including a nm-sized carbon atom structure having an excellentthermal conductivity (a diamond, a fullerene, a carbon nanotube or thelike).(d) In the above (a), the columnar heat sink 3 has a nanocompositestructure including a metal/alloy component having a nanocompositecrystal structure and a nm-sized carbon atom structure having anexcellent thermal conductivity (a diamond, a fullerene, a carbonnanotube or the like).(e) The through electrode 2 is a casting formed by using the via 20formed in the substrate 1 as a mold, while the columnar heat sink 3 hasa nanocomposite structure including a metal/alloy component having ananocomposite crystal structure and is a casting formed by using the via30 formed in the substrate 1 as a mold. It is not necessarily requiredthat the through electrode 2 includes a carbon nanotube.(f) In the above (e), the columnar heat sink 3 has a nanocompositestructure including a nm-sized carbon atom structure having an excellentthermal conductivity (a diamond, a fullerene, a carbon nanotube or thelike).(g) The through electrode 2 is a casting formed by using the via 20formed in the substrate 1 as a mold, while the columnar heat sink 3 hasa nanocomposite structure including a nm-sized carbon atom structurehaving an excellent thermal conductivity (a diamond, a fullerene, acarbon nanotube or the like). It is not necessarily required that thethrough electrode 2 includes a carbon nanotube.

As shown in FIG. 9, the above-described substrate 1 can be combined withan electronic component 6 to provide an electronic device. Theelectronic component 6 is mounted on the substrate 1 with its electrodebonded to the through electrode 2. Thus, an electrical circuit can bemade for the electronic component 6 using the through electrode 2 havinga low electrical resistance, while heat generated by the operation ofthe electronic component 6 can be efficiently dissipated through thecolumnar heat sink 3, thereby avoiding characteristic change,malfunction and even thermal runaway due to the heat generation of theelectronic component 6.

In the present invention, the electronic component may be an activeelement, a passive component or a composite element thereof. Typicalexamples of the active element include a light-emitting diode, varioustypes of memories, various types of logic ICs and an analog circuitelement. Examples of the passive component include a capacitor, aninductor, a resistor or a composite element thereof.

In the present invention, the electronic device may be almost anyelectrical product based on the technology of the electronics. Specificexamples include a personal computer, a mobile phone, a digitalappliance, a light-emitting device using a light-emitting diode, alighting apparatus, a traffic light, an image processing device, animage sensor and a vehicle-mounted electronic device. It may also be onehaving a three-dimensional multilayer structure based on the TSVtechnology or one having a three-dimensional multilayer structureconstructed by combining an interposer and various types of elements.Next will be described specific embodiments of electronic components andelectronic devices. In any illustrative embodiment, through electrodesand columnar heat sinks have the same features and effects as describedabove, so that duplicate explanations are omitted.

Embodiment 1 Light-Emitting Diode and Light-Emitting Device

A light-emitting device shown in FIGS. 10 to 12 comprises a substrate 1and a light-emitting element 6. The light-emitting element 6 is coveredwith a fluorescent layer 7. The substrate 1 serves as a so-calledpackage, includes two through electrodes 2, 2 and a number of columnarheat sinks 3 and has a cavity 11 at one side thereof. Preferably, thesubstrate 1 includes Si as a main component. Alternatively, thesubstrate 1 may be an insulating resin substrate or an insulatingceramic substrate. In the figures, the substrate 1 has a rectangularoutline but its shape is arbitrary. The cavity 11 of the substrate 1 isformed to surround the through electrodes 2, 2 at a distance, wherein areflection film 8 such as an Al film, an Ag film or a Cr film is formedalmost all along its inner side face by sputtering or the like. It isalso possible to form an insulating film such as an oxide film beneaththe reflection film 8.

The through electrodes 2, 2 each pass through the substrate 1 in thethickness direction within the area of the cavity 11 to have one endexposed on one side within the cavity 11 and the other end exposed onthe other side of the substrate 1. The through electrodes 2, 2 are asolid column and may have any arbitrary section such as a polygonalshape or a circular shape. The through electrodes 2, 2 may havedifferent planar shapes between a portion passing through the substrate1 and a portion located on one surface of the substrate 1 and intendedto be bonded to the light-emitting element 6. For example, the portionpassing through the substrate 1 is shaped to have a polygonal section, acircular section or the like, while the portion intended to be bonded tothe light-emitting element 6 is shaped to have an increased plane area.Moreover, the through electrodes 2, 2 preferably have an end face shapedin accordance with an electrode of a light-emitting element 6 to beconnected. In the present embodiment, from this viewpoint, one of thethrough electrodes 2, 2 has a circular end face, while the other has arectangular end face.

Many columnar heat sinks 3 passing through the substrate 1 in thethickness direction are arranged at a small distance from each other inthe form of matrix. The columnar heat sinks 3 are connected togetherthrough a heat dissipation layer 31 provided on a back surface (secondsurface) of the substrate 1. The through electrodes 2, 2 are independentof the heat dissipation layer 31. The heat dissipation layer 31 is notlimited to the illustrated film form but may have a three-dimensionalstructure having an enlarged heat dissipation area.

The light-emitting element 6 is a light-emitting diode, and the oneillustrated in FIGS. 13 and 14 has a semiconductor multilayer structure61 in which a P-type semiconductor layer 611 and an N-type semiconductorlayer 613 are stacked on a surface opposite from a light-emittingsurface 60 of a transparent crystal layer 62. Between the P-typesemiconductor layer 611 and the N-type semiconductor layer 613 isdisposed an active layer 612.

Of the P-type semiconductor layer 611 and the N-type semiconductor layer613, the N-type semiconductor layer 613 lying closer to the transparentcrystal layer 62 has a portion 614 not coinciding with the P-typesemiconductor layer 611, and an N-side electrode 63 is disposed on thesurface of the noncoinciding portion 614. A P-side electrode 64 isdisposed on the surface of the P-type semiconductor layer 611 at acoinciding portion. The N-side electrode 63 is not limited to thecircular shape but may have a polygonal shape.

In the present embodiment, the plane area of the N-side electrode 63disposed on the noncoinciding portion 614 is smaller than that of theP-side electrode 64 disposed on the coinciding portion. Regarding theelectrode width as seen in an arrangement direction of the N-sideelectrode 63 and the P-side electrode 64, more specifically, the N-sideelectrode 63 has a smaller electrode width than the P-side electrode 64.With the electrodes thus arranged, the width of the noncoincidingportion 614 can be decreased to thereby increase the width and area ofthe coinciding portion which will serve as a light-emitting area, sothat the light emission amount can be increased.

However, FIGS. 13 and 14 show just an example of the light-emittingelement 6 applicable to the present invention, and it should not beconstrued as limitative. For example, it may be constructed such thatthe transparent crystal layer 62 and the semiconductor multilayerstructure 61 are in an upside down relationship. Moreover, the electrodearea can be determined in consideration of current diffusion.

As shown in FIG. 10, the light-emitting element 6 is disposed within thecavity 11 of the substrate 1, wherein the P-side electrode 64 of theP-type semiconductor layer 611 is connected to one end of one throughelectrode 2, while the N-side electrode 63 of the N-type semiconductorlayer 613 is connected to one end of the other through electrode 2. Whenput in the cavity 11, the light-emitting element 6 is disposed with itsupper surface lower than the surface of the substrate 1 around thecavity 11. Then, the fluorescent layer 7 is filled therein in such amanner as to eliminate the gap.

The P-side electrode 64 and the N-side electrode 63 are opposed to eachother at a distance. Upon bonding the P-side electrode 64 and onethrough electrode 2 and bonding the N-side electrode 63 and the otherthrough electrode 2, a junction film is interposed at a junctioninterface between them. The junction film comprises at least onelow-melting point metal component selected from the group consisting ofSn, In, Bi Ga and Sb and a high-melting point metal material includingat least one component selected from the group consisting of Cr, Ag, Cu,Au, Pt, Pd, Ni, an Ni—P alloy and an Ni—B alloy. Since the low-meltingpoint metal can be consumed by reacting with the P-side electrode 64 andone through electrode 2 or the N-side electrode 63 and the other throughelectrode 2 and forming an intermetallic compound, the melting pointincreases considerably after the bonding.

Typically, the transparent crystal layer 62 comprises sapphire and itsone side becomes the light-emitting surface 60. A buffer layer (notshown) lies on one side of the transparent crystal layer 62, and thesemiconductor multilayer structure 61 is grown over the transparentcrystal layer 62 with the buffer layer therebetween.

The semiconductor multilayer structure 61 is well-known regarding thelight-emitting element 6. It has a PN junction and typically comprises aIII-V group compound semiconductor. However, it is not limited to theknown art but can comprise any compound semiconductors that may besuggested in future.

In the present invention, the light-emitting element 6 may be any one ofred, green, blue and orange light-emitting elements or a whitelight-emitting element. Semiconductor materials for constituting thesemiconductor multilayer structure 61 in these light-emitting elementsand their manufacturing methods are well known in the art.

In the illustrated light-emitting device, the substrate 1 includes twothrough electrodes 2, 2 and has the cavity 11 at one side thereof. Thethrough electrodes 2, 2 each pass through the substrate 1 in thethickness direction to have one end exposed on one side within thecavity 11. The light-emitting element 6 is disposed within the cavity 11of the substrate 1. In the present embodiment, the light-emittingelement 6 is constructed such that the P-type semiconductor layer 611and the N-type semiconductor layer 613 are stacked on the second surfaceopposite from the first surface 60 which will become the light-emittingsurface of the transparent crystal layer 62. Inside the cavity 11,moreover, the P-side electrode 64 of the P-type semiconductor layer 611is connected to one end of one through electrode 2, while the N-sideelectrode 63 of the N-type semiconductor layer 613 is connected to oneend of the other through electrode 2. According to the presentembodiment, therefore, current can be supplied to the light-emittingelement 6 from the side opposite from the side having the transparentcrystal layer 62, thereby realizing a structure in which the electrodesfor the light-emitting element 6 do not appear on the light-emittingsurface 60. Thus, produced light can be efficiently emitted to theoutside.

The substrate 1 includes many columnar heat sinks 3. The columnar heatsinks 3 are provided to extend in the thickness direction of thesubstrate 1. Accordingly, heat generated by the light emitting operationof the light-emitting element 6 can be dissipated to the outside of thesubstrate 1 through the columnar heat sinks 3, keeping the bondingstrength at the junction where the electrodes 63, 64 of thelight-emitting element 6 are connected to the through electrodes 2, 2and maintaining the reliability of electrical connection. Moreover, avariation in light-emitting characteristics of the light-emittingelement 6 due to the heat generation can be avoided.

The columnar heat sink 3 has one end led to the second surface of thesubstrate 1 and connected to the heat dissipation layer 31 provided onthe second surface of the substrate 1. With this structure, the heatdissipation characteristics can be further improved.

In the present embodiment, the reflection film 8 is provided between theinner surface of the cavity 11 and the side face of the light-emittingelement 6. Therefore, light produced at the semiconductor layer 61 canbe led to the light-emitting surface 60 of the transparent crystal layer62 while suppressing light scattering and absorption due to thetransparent crystal layer 62.

The reflection film 8 may be adhered to the inner surface of the cavity11 or adhered to the side face of the light-emitting element 6. In theembodiment shown in FIGS. 10 to 12, the light-emitting element 6 isfitted in the cavity 11 with a small clearance. With this structure,positioning and setting of the light-emitting element 6 with respect tothe substrate 1 can be performed easily and reliably.

Although not illustrated, the light-emitting surface 60 may have atransparent optical component having small irregularities. This enablesthe light-emitting surface 60 to diffuse or disperse light, achievinguniform surface light emission. Instead of providing the transparentoptical component, it is also possible to form the light-emittingsurface 60 with small irregularities. Although not illustrated,furthermore, the light-emitting surface 60 may have a fluorescent bodyalong with or without the small irregularities.

Referring further to FIG. 15, there is illustrated a light-emittingdevice whose cavity 11 has an increased plane area as compared with theembodiment shown in FIGS. 10 to 12. The cavity 11 is considerably largerthan the plane area of the light-emitting element 6, wherein thefluorescent layer 7 or the like is filled in a space between theperiphery of the light-emitting element 6 and the inner wall surface ofthe cavity 11. Moreover, the reflection film 8 is adhered to the innerwall surface of the cavity 11. The columnar heat sink 3 has one end(upper end) terminated at almost the same height as the bottom face ofthe cavity 11 and the other end led to the back surface of the substrate1 and connected to the heat dissipation layer 31.

Referring to FIG. 16, there is illustrated a light-emitting devicehaving almost the same structure as that of FIG. 15, wherein aprotrusion 12 is provided at the center of the cavity 11 and thelight-emitting element 6 is mounted on the protrusion 12. Theembodiments of FIGS. 15 and 16 also have the effects described withreference to FIGS. 10 to 13.

The light-emitting device according to the present invention hasnumerous uses such as a light-emitting diode being a singlelight-emitting element, a surface light-emitting device having aplurality of light-emitting elements arranged, for example, in the formof matrix, a lighting apparatus, a backlight for a liquid crystaldisplay, a signal light and so on. Their examples will be describedbelow.

FIG. 17 is a plan view of a lighting apparatus having a light-emittingdiode. The illustrated lighting apparatus has a rectangular substrate 1and a plurality of light-emitting devices Q arranged on the substrate 1in the form of matrix.

The light-emitting devices Q each have a light-emitting element 6 foremitting a light of a given hue, two through electrodes 2, 2 forelectrical connection of the light-emitting element 6 and many columnarheat sinks 3 arranged around the light-emitting element 6. Eachlight-emitting element 6 is disposed within a cavity 11 formed in thesubstrate surface of a substrate 1. The shape of the substrate 1, thenumber and arrangement of the light-emitting devices Q and the numberand arrangement of the columnar heat sinks 3 are not limited to theembodiment shown in FIG. 17 but can be determined as appropriate.

The above-described light-emitting devices Q are shown in more detail inFIGS. 18 to 20. The substrate 1 serves as a so-called package, includinga plurality of through electrodes 2 and a plurality of columnar heatsinks 3 and having cavities 11 in its substrate surface. For thesubstrate 1, it is preferable to use a substrate including Si as a maincomponent, but it is not limited thereto and an insulating resinsubstrate or an insulating ceramic substrate may also be used.Furthermore, it may be a conductive substrate such as a metal substrate.In the present embodiment, description will be made concerning the casewhere the substrate 1 is an Si substrate.

The shape of the cavity 11 of the substrate 1 is not limited to thecuboid shape shown in FIG. 17, but it may have other shapes. The cavity11 is formed to surround the through electrodes 2, 2 at a distance asseen in plan, wherein a reflection film 8 is formed almost all along itsinner side face by sputtering or the like. The reflection film 8 is notlimited to the above embodiment but may be adhered to the side face ofthe light-emitting element 6, for example, and it is also possible toform an insulating film such as an oxide film beneath the reflectionfilm 8.

The light-emitting element 6 is fitted in the cavity 11 with a smallclearance. With this structure, positioning and setting of thelight-emitting element 6 with respect to the substrate 1 can beperformed easily and reliably. Moreover, the upper surface of thelight-emitting element 6 within the cavity 11 is covered with thefluorescent layer 7. This improves the luminance of light emitted fromthe light-emitting element 6. Examples of fluorescent materials to beused for the fluorescent layer 7 include calcium phosphate. The hue ofthe fluorescent layer 7 may be determined as appropriate depending onthe intended use.

The through electrodes 2, 2 each pass through the substrate 1 in thethickness direction in the bottom face of the cavity 11 to have one endexposed on one side within the cavity 11 and the other end exposed onthe other side of the substrate 1. The through electrodes 2, 2 may havean end face shaped in accordance with an electrode of the light-emittingelement 6 to be connected, and in this case, the through electrodes 2, 2have a circular end face and a rectangular end face, respectively.

In the present embodiment, since the substrate 1 is a conductive Sisubstrate, the through electrodes 2, 2 are electrically insulated fromthe substrate 1. As a means for electrical insulation, an electricalinsulating layer 9 is provided between the periphery of the throughelectrodes 2, 2 and the inner wall surface of the vias containing thethrough electrodes 2, 2. The electrical insulating layer 9 may be anoxide film or a nitride film obtained by oxidizing or nitriding theinner wall surface of the via in the substrate 1 being an Si substrateor a layer of an organic insulating material or an inorganic insulatingmaterial such as glass filled into the via.

Many columnar heat sinks 3 passing through the substrate 1 in thethickness direction are arranged at a small distance from each other inthe form of matrix and connected to the heat dissipation layer 31provided on the back surface (second surface) of the substrate 1. Thus,the columnar heat sinks 3 can effectively dissipate heat from thesubstrate 1.

The heat dissipation layer 31 comprises a material having a relativelyhigh thermal conductivity such as aluminum and can be disposed on theback surface of the substrate 1 as a plurality of separate members or asa single member to be connected in common to all the heat sinks 3.Furthermore, the heat dissipation layer 31 is not limited to theillustrated film form but may have a three-dimensional structure havingan increased heat dissipation area.

FIG. 20 shows another embodiment of the light-emitting devices Q. Thedifference between the light-emitting device according to the presentembodiment and the foregoing embodiment resides in that the substrate 1comprises three layers 101 to 103 and that the cavity 11 has anincreased plane area.

In the present embodiment, the substrate 1 is an SOI substrateconstructed by stacking a first silicone layer 101 comprising a firstsubstrate layer, an oxide layer 102 comprising an insulating layer, anda second silicon layer 103 comprising a second substrate layer in thementioned order.

The cavity 11 is formed by cutting off the surface of the second siliconlayer 103 and has an inner side face which is inclined to increase theopening area toward the open end. The cavity 11 has a considerablylarger plane area than the light-emitting element 6, wherein thefluorescent layer 7 is filled in a space between the periphery of thelight-emitting element 6 and the inner wall surface of the cavity 11.Moreover, the reflection film 8 is adhered to the inner wall surface ofthe cavity 11 as in the foregoing embodiment.

The through electrodes 2, 2 pass through the first silicon layer 101 inan electrically insulated state because of the electrical insulatinglayer 9 and have their cavity 11-side ends connected to connections 41,42 passing through the oxide layer 102, respectively. The connections41, 42 are connected to two terminals 601, 602 of the light-emittingelement 6. The connections 41, 42 are not limited to a cylindrical shapebut may have other shapes such as a square pole shape.

The columnar heat sinks 3 are provided to pass through the firstsilicone layer 101 in the thickness direction of the substrate 1 in thesame manner as the through electrodes 2, 2 and connected to the heatdissipation layer 31. That is, the columnar heat sinks 3 are provided toextend from the back surface of the substrate 1 to the interface betweenthe first silicon layer 101 and the oxide layer 102. With thisstructure, the oxide layer 102 can serve as an etching blocking layerduring formation of the columnar heat sinks 3. This leads to anadvantage that the etching process can be controlled extremely easilybecause the height of the columnar heat sink 3 can be defined by thefilm thickness of the first silicon layer 101.

The above-described lighting apparatus includes the substrate 1, and thesubstrate 1 includes many columnar heat sinks 3. Since the columnar heatsinks 3 are provided to extend in the thickness direction of thesubstrate 1, heat generated by the light emitting operation of thelight-emitting element 6 can be dissipated to the outside of thesubstrate 1 through the columnar heat sinks 3, keeping the bondingstrength at the junction where the terminals 601, 602 of thelight-emitting element 6 are connected to the through electrodes 2, 2and maintaining the reliability of electrical connection, and alsoavoiding a variation in light-emitting characteristics of thelight-emitting element 6 due to the heat generation.

Since the columnar heat sink 3 has one end led to the second surface ofthe substrate 1 and connected to the heat dissipation layer 31 providedon the second surface of the substrate 1, the heat dissipationcharacteristics of the substrate 1 can be further improved.

The light-emitting element 6 is the one shown in FIGS. 13 and 14.Therefore, current can be supplied to the light-emitting element 6 fromthe side opposite from the transparent crystal layer 62 in the stackingdirection, thereby realizing a structure in which the terminals 601, 602of the light-emitting element 6 do not appear on the light-emittingsurface, so that produced light can be efficiently emitted to theoutside. Moreover, the light produced at the semiconductor layer 61 canbe effectively led to the light-emitting surface of the transparentcrystal layer 62 because the reflection film 8 can suppress lightscattering and absorption due to the transparent crystal layer 62.

Next will be described a liquid crystal display according to the presentinvention with reference to FIG. 22. The liquid crystal display includesa liquid crystal panel 120 and a backlight 130. Conceptually, thisliquid crystal display is not limited to a common display device forcomputers or a liquid crystal display for general-purpose appliances butcan also be used for a liquid crystal television or a portableelectronic device such as a mobile phone, a handheld game console or apersonal digital assistant.

The liquid crystal panel 120 is a liquid crystal module comprising apolarizing filter, a glass substrate, a liquid crystal layer and so onand driven by electrical signals from a driving circuit (not shown)based on image signals. The backlight 130 is the lighting apparatusshown in FIGS. 17 to 21 and illuminates the liquid crystal panel 120from the back side with a plurality of the light-emitting devices Q.However, the backlight 130 is not limited to this embodiment and, forexample, may be the lighting apparatus shown in FIGS. 10 to 16, and itgoes without saying that any type of lighting apparatus according to thepresent invention can be used.

In the backlight 130, the through electrodes 2, 2 are connected to apower supply through a bump electrode and a wiring substrate, wherebythe light-emitting element 6 supplied with power can irradiate light tothe liquid crystal panel 120. On the other hand, the columnar heat sinks3 are connected to the heat dissipation layer 31 so as to expel heatinside the substrate 1 toward the back surface of the liquid crystaldisplay.

The liquid crystal display according to the present invention also hasthe foregoing effects because of including the above-described lightingapparatus.

Next will be described a light-emitting diode display according to thepresent invention with reference to FIGS. 23 and 24. Since thelight-emitting diode display uses the light-emitting element itself as apixel, it does not need a backlight and therefore has the advantage ofbeing able to reduce power consumption.

FIG. 23 shows a pixel Q of the light-emitting diode display as seen inplan, while FIG. 24 shows the light-emitting diode display in which thepixels Q are arranged in the form of matrix on the substrate 1.

The single pixel Q has three light-emitting devices QR, QG, QB, whereinthese light-emitting devices QR, QG, QB have a light-emitting element 6Rfor emitting a red light, a light-emitting element 6G for emitting agreen light and a light-emitting element 6B for emitting a blue light,respectively. The light-emitting diode display according to the presentembodiment is intended to be a full-color display and therefore includesthe light-emitting elements 6R, 6G, 6B for three colors, but it is notlimited thereto. If it is intended to be a single-color display, forexample, the pixel Q may include only one of the light-emitting elements6R, 6G, 6B for three colors. That is, the pixel Q can be constructed byappropriately selecting the light-emitting devices QR, QG, QB having alight-emitting element based on its display function.

In the pixel Q of the present embodiment, moreover, the threelight-emitting devices QR, QG, QB are located at vertexes of a triangleas illustrated, but they are not limited thereto and may be arranged asappropriate depending on the characteristics of the light-emittingelements 6R, 6G, 6B for three colors.

In the light-emitting diode display according to the present invention,the through electrodes 2, 2 of each light-emitting element 6R, 6G, 6Bare connected to a thin-film transistor (TFT) or the like, whereby lightemission of each pixel Q is controlled by a driving circuit depending onimage signals. On the other hand, the columnar heat sinks 3 areconnected to the heat dissipation layer 31 so as to expel heat insidethe substrate 1 toward the back surface of the display, as in thestructure shown in FIGS. 18 to 23.

The light-emitting diode display according to the present invention alsohas the foregoing effects because of having the same structure as theabove-described lighting apparatus.

On the other hand, the signal light according to the present inventionis intended for use in a railroad signal or a traffic light, forexample, and constructed by arranging many light-emitting devices QR,QG, QB to have the light-emitting elements 6R, 6G, 6B, for example, fortwo or more colors, as in the above-described light-emitting diodedisplay.

The signal light according to the present invention also has theforegoing effects because of having the same structure as theabove-described lighting apparatus.

The substrate 1 shown in FIG. 25 has the through electrodes 2, thecolumnar heat sinks 3 and the cavity 11. In the present embodiment, theillustrated substrate 1 is an SOT substrate constructed by stacking afirst silicone layer 101 comprising a first substrate layer, an oxidelayer 102 comprising an insulating layer, and a second silicon layer 103comprising a second substrate layer in the mentioned order.

Regarding the manufacturing method, there have been known two types ofSOI substrate: SIMOX (separation by implantation of oxygen)-type andwafer bonding-type. Any type of SOI substrate can be used. For theSIMOX-type SOI substrate, there has been known a technique of forming aninsulating layer of oxidized silicon within a silicon crystal by buryingoxygen molecules from the silicon crystal surface using ion implantationand then oxidizing it at a high temperature. Such an insulating layer isreferred to as buried oxide (BOX) layer.

The cavity 11 is a portion to which an electronic element is to beattached and formed in the surface of the second silicon layer 103. Theillustrated cavity 11 is formed by cutting off the center of the secondsilicon layer 103 in a rectangular shape and has an inner side facewhich is inclined to increase the opening area toward the open end. Thesecond silicon layer 103 and the inner surface of the cavity 11 arecovered with an insulating layer 132. The insulating layer 132 may be asilicon oxide film or a silicon nitride film.

The through electrode 2 passes through the first silicone layer 101 andthe oxide layer 102 and is exposed with one end projecting slightly fromthe bottom face of the cavity 11. More specifically, the throughelectrode 2 comprises a terminal portion (bump) 21 to be used as aconnection to the outside, a through portion 22 passing through thefirst silicone layer 101 and an element-connecting portion 23 to beconnected to a terminal electrode of an electronic element. The terminalportion 21 is adhered to one end face of the through portion 22 and maybe an electroless plating film such as of Ti—Au.

In the embodiment where the SOI substrate is used as the substrate 1, aninsulating film 111 is provided between the first silicone layer 101 andthe through electrode 2 and on the surface of the first silicone layer101. The insulating film 111 may be a silicon oxide film or a siliconnitride film.

One end of the element-connecting portion 23 is adhered to one end ofthe through portion 22, while the other end passes through theinsulating film 111, the oxide layer 102 and the insulating layer 132adhered to the bottom face of the cavity 11 and projects into the cavity11 for exposure. The element-connecting portion 23 may also be anelectroless plating film such as of Ti—Au as with the terminal portion21.

On the other hand, the columnar heat sinks 3 are each filled in a via113 formed in the thickness direction of the first silicone layer 101.The columnar heat sink 3 comprises a columnar portion 301 being a mainpart and a terminal portion 302 adhered to one end face thereof. Theterminal portion 302 may be an electroless plating film such as of Ti—Auas with the terminal portion 21. The vias 113 having the columnarportion 301 are provided to pass through the first silicone layer 101and terminate at the interface between first silicone layer 101 and theoxide layer 102 and are distributed around the cavity 11 to have a givenoccupancy rate as the substrate 1 is seen in plan.

Between the columnar heat sink 3 and the first silicone layer 101, thereis provided the insulating film 111 being a silicon oxide film or asilicon nitride film.

Referring to FIG. 26, there is illustrated a light-emitting devicehaving the substrate 1 shown in FIG. 25. In this light-emitting device,a light-emitting element (LED) 6 being an electronic element is disposedin the cavity 11 of the circuit substrate. The light-emitting element 6has an electrode bonded to the element-connecting portion 23 of thethrough electrode 2. Although not illustrated, the insulating layer 132inside the cavity 11 is preferably provided with a light reflectionfilm.

Here, the substrate 1 has the cavity 11 and the through electrodes 2,the cavity 11 is formed in the surface of the second silicon layer 103,and the through electrode 2 passes through the first silicon layer 101and the oxide layer 102 to have one end exposed on the bottom face ofthe cavity 11. Therefore, the light-emitting element 6 being anelectronic element can be disposed within the cavity 11 of the circuitsubstrate and the electrode provided on one surface of thelight-emitting element 6 can be bonded to the element-connecting portion23 forming one end of the through electrode 2. Thus, the light-emittingelement 6 can be connected to the through electrode 2 by a flip chipbonding process.

Furthermore, the circuit substrate according to the present inventionincludes the columnar heat sink 3, and the columnar heat sink 3 isfilled in the via 113. The via 113 passes through the first siliconlayer 101. Accordingly, heat generated by the operation of thelight-emitting element 6 can be dissipated to the outside of thesubstrate 1 through the columnar heat sinks 3, keeping the bondingstrength at the portion where the light-emitting element 6 is bonded tothe through electrode 2 and maintaining the reliability of electricalconnection. Moreover, a variation in electrical characteristics of thelight-emitting element 6 due to the heat generation can be avoided.

The via 113 is provided to pass through the first silicon layer 101 andterminate at the interface between the first silicon layer 101 and theoxide layer 102. With this structure, the oxide layer 102 can serve asan etching blocking layer during formation of the via 113. This makes itextremely easy to control the depth of the via 113 because the depth ofthe via 113 has a uniform value defined by a depth from the firstsilicon layer 101 to the oxide layer 102, i.e., the film thickness ofthe first silicon layer 101.

The vias 113 are distributed around the cavity 11 to have a givenoccupancy rate as the substrate 1 is seen in plan. This means that aheat dissipation area is formed to surround the electronic elementhoused in the cavity 11, i.e., the light-emitting element 6 with thecolumnar heat sinks 3, so that heat generated at the light-emittingelement 6 can be collected and dissipated efficiently.

Moreover, heat generated by the operation of the light-emitting element6 can be efficiently dissipated to the outside of the substrate 1through the columnar heat sinks 3 by properly selecting the thermalconductivity of the material constituting the columnar heat sinks 3 andthe occupancy rate of the columnar heat sinks 3.

Embodiment 2 Electronic Device or Electronic Equipment

The electronic element is not limited to the foregoing light-emittingelement 6 but may be an active element, a passive component or acomposite element thereof. It may also be one having the above-describedvarious types of elements arranged into a three-dimensional multilayerstructure based on the TSV technology or one having an interposer andthe various types of elements combined into a three-dimensionalmultilayer structure.

Referring to FIG. 27, there is illustrated a circuit substrate suitablefor mounting such an electronic element. In this figure, the componentsidentical or similar to those illustrated in the foregoing figures aredenoted by the same reference symbols. In FIG. 27, the number of throughelectrodes 2 is increased in accordance with the number of terminalelectrodes of an electronic element to be mounted within the cavity 11.In addition, the cavity 11 has an inner side face extendingsubstantially vertically.

FIG. 28 shows an electronic device in which an electronic element 6 isincorporated into the circuit substrate shown in FIG. 27. The electronicelement 6 has a three-dimensional multilayer structure based on the TSVtechnology, wherein a logic element 6A such as an LSI and a memoryelement 6C such as a DRAM are stacked and bonded through an interposer6B. Electronic devices of this type can be used as a basic element of aninformation processing system. More specifically, they can be used as acomponent of an image processing system in a personal digital assistant,a mobile phone, a digital appliance, a server or the like. There areother uses, including an image sensor module.

The logic element 6A is a so-called logic IC, and its electrodesprovided on one side are bonded to the element-connecting portions 23 ofthe through elements 2 provided in the substrate 1. The logic element 6Ais in the form of a chip containing a semiconductor logic circuit suchas an LSI. The logic element 6A may have a three-dimensional multilayerstructure in which the embedded semiconductor logic circuit is led tothe electrodes based on the TSV technology.

The interposer 6B has a plurality of through electrodes, wherein one endof the through electrode is connected to an electrode of the logicelement 6A, while the other end of the through electrode is connected toan electrode of the memory element 6C. The interposer 6B can be obtainedsuch that the through electrodes are formed in an Si substrate, a resinsubstrate or a ceramic substrate by using the same composition andmanufacturing process as the through electrodes of the circuitsubstrate.

The memory element 6C has an embedded memory cell connected to theelectrode. The memory element 6C may also have a three-dimensionalstructure in which the memory cell is led to the electrodes based on theTSV technology as in the logic element 6A.

However, the layer number and type of the elements 6A to BC constitutingthe electronic element 6, the arrangement of their electrodes and so oncan vary widely depending on the used electronic element 6, and FIG. 28merely shows one conceptual example of the three-dimensional multilayerstructure.

Basically, the electronic device shown in FIG. 28 has the same effectsas the electronic device shown in FIG. 26. In the electronic device ofFIG. 28, however, since the three-dimensional multilayer structure isemployed to improve the packaging density, the performance and theprocessing speed and reduce the size, the thickness and the weight, thequestion of how to dissipate heat generated by the operation becomes amore serious issue.

In the embodiment shown in FIG. 28, there is used the substrate 1 havingthe columnar heat sinks 3 in the thickness direction of the substrate 1,and the electronic element 6 is disposed in the cavity 11 formed in thesubstrate. Therefore, heat generated by the operation of the electronicelement 6 can be dissipated to the outside of the substrate 1 throughthe columnar heat sinks 3, thereby avoiding abnormal heat generation dueto heat accumulation, keeping the bonding strength between the throughelectrodes 2 of the substrate 1 and the electrodes of the logic element6A, the bonding strength between the electrodes of the logic element 6Aand the through electrodes of the interposer 6B and the bonding strengthbetween the through electrodes of the interposer 6B and the electrodesof the memory element 6C and maintaining the reliability of electricalconnection. Moreover, a variation in electrical characteristics of thelogic element 6A and the memory element 6C due to the heat generationcan be avoided.

The substrate 1 has the cavity 11 at one side thereof and containstherein the electronic element 6 having a three-dimensional multilayerstructure. Many columnar heat sinks 3 each passing through the substrate1 in the thickness direction are arranged around the cavity 11 tosurround the cavity 11 at a small distance from each other. This meansthat a heat dissipation pathway is formed by the columnar heat sinks 3to surround the electronic element 6 housed in the cavity 11 as seen inplan, so that heat generated at the electronic element 6 can becollected and dissipated efficiently.

FIG. 29 shows still another electronic device. In this figure, theportions corresponding to the components illustrated in the foregoingfigures are denoted by the same reference symbols and duplicateexplanations are omitted. In the illustrated electronic device, aplurality of through electrodes 2 each pass through the substrate 1 inthe thickness direction within the area of the cavity 11 to have one endexposed on one side within the cavity 11 and the other end exposed onthe other side of the substrate 1.

Around the cavity 11, many columnar heat sinks 3 passing through thesubstrate 1 in the thickness direction are arranged in the form ofmatrix at a small distance from each other. The columnar heat sinks 3have first ends (lower ends) connected together through a heatdissipation layer 31 provided on the back surface (second surface) ofthe substrate 1 and second ends (upper ends) led to the front surface ofthe substrate 1. The heat dissipation layer 31 is not limited to theillustrated film form but may have a three-dimensional structure havingan increased heat dissipation area.

The electronic element 6 is, for example, an active element such as asemiconductor chip, a passive component such as a capacitor or aninductor or a composite element thereof. The electronic element 6 mayhave a semiconductor element and a passive component in combination ormay be a memory element, a logic circuit element or an analog circuitelement. These elements may have a single-layer structure or amultilayer structure.

The illustrated electronic element 6 takes the form of a flip chiphaving a plurality of electrodes 601 on one surface intended to be amounting surface and is disposed within the cavity 11 of the substrate 1to have each electrode 601 bonded to one end of the through electrode 2.

The illustrated electronic device includes the substrate 1, and thesubstrate 1 includes many columnar heat sinks 3. The columnar heat sinks3 are provided to extend in the thickness direction of the substrate 1.Therefore, heat generated by the operation of the electronic element 6can be dissipated to the outside of the substrate 1 through the columnarheat sinks 3, keeping the bonding strength at the junction where theelectrodes 601 of the electronic element 6 are connected to the throughelectrodes 2 and maintaining the reliability of electrical connection.Moreover, a variation in electrical characteristics of the electronicelement 6 due to the heat generation can be avoided.

The substrate 1 has the cavity 11 at one side thereof and containstherein the electronic element 6. Many columnar heat sinks 3 eachpassing through the substrate 1 in the thickness direction are arrangedaround the cavity 11 to surround the cavity 11 at a small distance fromeach other. This means that a heat dissipation pathway is formed by thecolumnar heat sinks 3 to three-dimensionally surround the electronicelement 6 housed in the cavity 11, so that heat generated at theelectronic element 6 can be collected three-dimensionally and dissipatedefficiently.

The columnar heat sink 3 passes through the substrate 1 in the thicknessdirection to have one end led to the second surface of the substrate 1and connected to the heat dissipation layer 31 provided on the secondsurface of the substrate 1. With this structure, the heat dissipationcharacteristics can be further improved.

In the embodiment shown in FIG. 29, the electronic element 6 is fittedin the cavity 11 with a small clearance. With this structure,positioning and setting of the electronic element 6 with respect to thesubstrate 1 can be performed easily and reliably.

Next description will be made with reference to FIG. 30. In the figure,the portions corresponding to the components illustrated in theforegoing figures are denoted by the same reference symbols andduplicate explanations are omitted. In the figure, the electronicelement 6 has a three-dimensional multilayer structure based on the TSVtechnology, wherein a logic element 6A such as an LSI and a memoryelement 6C such as a DRAM are stacked and bonded through an interposer6B. That is, it has a similar structure to that shown in FIG. 28.

The interposer 6B has many through electrodes 2B arranged at a distancefrom each other, wherein one end of the through electrode 2B isconnected to an electrode 412 of the logic element 6A, while the otherend of the through electrode 2B is connected to an electrode 431 of thememory element 6C. The interposer 6B can be obtained such that thethrough electrodes 2B are formed in an Si substrate, a resin substrateor a ceramic substrate by using the same composition and manufacturingprocess as the through electrodes 2.

The substrate 1 has the cavity 11 at one side thereof and containstherein the electronic element 6 having a three-dimensional multilayerstructure. Many columnar heat sinks 3 each passing through the substrate1 in the thickness direction are arranged around the cavity 11 tosurround the cavity 11 at a small distance from each other. This meansthat a heat dissipation pathway is formed by the columnar heat sinks 3to three-dimensionally surround the electronic element 6 housed in thecavity 11, so that heat generated at the electronic element 6 can becollected three-dimensionally and dissipated efficiently.

The columnar heat sink 3 passes through the substrate 1 in the thicknessdirection to have one end led to the second surface of the substrate 1and connected to the heat dissipation layer 31 provided on the secondsurface of the substrate 1. With this structure, the heat dissipationcharacteristics can be further improved.

Embodiment 3 Multilayer Electronic Device

Then, FIG. 31 shows an electronic device 1 comprising a plurality ofstacked substrates 101 to 103. In the figure, the lowermost firstsubstrate 101 is an Si substrate, a ceramic substrate, a glass-epoxysubstrate or the like and intended to support the other substrates 102,103. The second substrate 102 is an interposer located between the firstsubstrate 101 and the third substrate 103 and includes a capacitorelement 230 such as a decoupling capacitor. The third substrate 103 isan IC chip including an integrated circuit 233 such as an arithmeticelement. The second and third substrates 102, 103 may be an Sisubstrate. It should be noted that since FIG. 31 shows a part of themultilayer structure on an enlarged scale, the IC chip is shown onlypartially.

The first to third substrates 101 to 103 are stacked with theirsubstrate surfaces in face-to-face contact with each other and includeone or more through electrodes 2. The through electrode 2 is acontinuous conductor extending across the first to third substrates 101to 103. More specifically, the through electrode 2 is provided in thefirst to third substrates 101 to 103 in an embedded state tocontinuously pass through them in the stacking direction.

In the present embodiment, all the through electrodes 2 continuouslypass through the first to third substrates 101 to 103, but it is alsopossible that some of them pass through only one or two substrates. Forexample, they may include a through electrode passing through the firstand second substrates 101, 102 but not passing through the thirdsubstrate 103.

The through electrode 2 is electrically connected to the capacitorelement 230 and the integrated circuit 233, individually. The capacitorelement 230 comprises a dielectric layer 234, an upper electrode layer232 and a lower electrode layer 236. With the dielectric layer 234therebetween, the upper electrode layer 232 and the lower electrodelayer 236 are extended and electrically connected to the right and leftthrough electrodes 2 in the figure. The integrated circuit 233 is alsoelectrically connected to the through electrodes 2 with electrodes 231,235 extending to the right and left through electrodes 2. Such aconnecting structure can be adopted when the capacitor element 230 isused as a decoupling capacitor for removing power noise of theintegrated circuit 233, for example.

In the electronic device according to the present invention, asdescribed above, the through electrodes 2 being a continuous conductorextending across two or more substrates 101 to 103 are provided with thesubstrate surfaces of the substrates 101 to 103 in face-to-face contactwith each other. That is, the electronic device according to the presentinvention has a structure in which two or more of substrates 101 to 103are stacked without using bumps. According to the present invention,therefore, there can be realized a high-quality, highly-reliableelectronic device which solves all the problems due to the use of a bumpbonding structure, such as difficulty in positioning, guarantee ofbonding strength and guarantee of heat resistance.

FIG. 32 shows another embodiment. In the embodiment shown in FIG. 32,the columnar heat sinks 3 are provided instead of or along with thethrough electrodes 2. The columnar heat sinks 3 are arranged around theintegrated circuit 233. This means that a heat dissipation pathway isformed by the columnar heat sinks 3 to surround the integrated circuit233 as the third substrate 103 is seen in plan, so that heat generatedat the integrated circuit 233 can be collected and dissipatedefficiently. When the integrated circuit 233 is an arithmetic element tobe used for a high-heat-generating CPU or the like, the provision of thecolumnar heat sinks 3 is particularly effective from the viewpoint ofensuring operation stability or the like.

The columnar heat sinks 3 are distributed with a given occupancy rate.By appropriately determining the occupancy rate of the columnar heatsinks 3 in consideration of the thermal resistance of the materialconstituting the columnar heat sinks 3, accordingly, heat generated bythe operation of the integrated circuit 233 can be efficientlydissipated to the outside of the electronic device 1 through thecolumnar heat sinks 3, thereby avoiding abnormal heat generation.

Since the columnar heat sink 3 is also a continuous body extendingacross two or more of the plurality of substrates 101 to 103, it makesit possible to solve all the problems that are inevitable when using abump bonding structure for the columnar heat sinks 3, such as difficultyin positioning, guarantee of bonding-strength and guarantee of heatresistance.

Embodiment 3 Other Devices

Referring to FIG. 33, there is illustrated a substrate having a numberof columnar heat sinks 3. In this substrate 1, the tip of the columnarheat sink 3 is kept within a heat-resistant insulating organic orinorganic substrate 1, thereby leaving an insulating layer having athickness of ΔH1 above it. That is, the columnar heat sink 3 is notrequired to pass through it. The thickness of ΔH1 can be determinedarbitrarily.

Referring next to FIG. 34, there is illustrated a substrate 1 comprisingan organic insulating substrate. The organic substrate 1 preferablycomprises a heat-resistant material. Particularly preferred is onehaving a heat resistance of 300° C. or more. The organic substrate 1has, on at least one side thereof, a metal layer 31, 32 such as of a Cufoil. The illustrated organic substrate 1 is a double-sided copper-cladsubstrate having the metal layers 31, 32 of a Cu foil on both sidesthereof. Various types of such a double-sided copper-clad substrate aresupplied from different board makers and put on the market, for example,under the name of high heat resistance glass-epoxy copper-cladsubstrate, high heat resistance low thermal expansion glass fabric basematerial epoxy resin copper-clad substrate, high thermal conductivityglass composite substrate, high heat resistance paper phenol copper-cladsubstrate, paper base phenolic resin copper-clad substrate and so on.

The use of the organic substrate 1 has advantages that a circuitsubstrate that has been already put into practical use and commerciallyavailable can be utilized, that the material cost for the substrate canbe reduced and that the via drilling process for the columnar heat sinks3 can be performed in short time.

Moreover, since the metal layer 31, 32 is provided on at least one sidethereof, the surface of the organic substrate 1 can be prevented fromcoming into direct contact with and being thermally damaged by a moltenmetal by feeding the molten metal from the side having the metal layer31, 32 during a common process including a heat treatment in thecolumnar heat sink-forming process.

Furthermore, since the metal layer 31, 32 is provided on a planeperpendicular to the columnar heat sinks 3, there is created not only aheat dissipation pathway in the thickness direction because of thecolumnar heat sinks 3 but also a heat dissipation and diffusion surfaceperpendicular to the heat dissipation pathway because of the metal layer31, 32. That is, a three-dimensional heat dissipation pathway can beformed to improve the heat dissipation characteristics.

Referring further to FIG. 35, there is illustrated a heat dissipationsubstrate having a structure in which a plurality of organic substrates1 having a metal layer 31, 32 on at least one side thereof are stackedwith the metal layers 31, 32 located at an interface. The number oforganic substrates 1 to be stacked can be determined arbitrarily.Preferably, adjacent organic substrates 1 are bonded together through abonding material having an excellent heat resistance and thermalconductivity.

In this structure, since the metal layers 31, 32 to be used as a heatdissipation pathway are provided at a middle portion of the stackedorganic substrates 1, there is created a three-dimensional heatdissipation structure in which in addition to heat dissipation throughthe columnar heat sinks 3, heat transferred from the columnar heat sinks3 can be dispersed in a planar direction at the middle portion of thesubstrates 1. Thus, heat can be prevented from being accumulated withinthe substrates 1, thereby suppressing temperature rise of an electroniccomponent to be mounted on the substrates 1. Preferably, the columnarheat sinks 3 are connected to the columnar heat sinks 3 and directlythermally coupled together.

The substrates shown in FIGS. 33 to 35 are useful as a heat dissipationsubstrate, but they may have various forms in addition to those shown inFIGS. 33 to 35. Such examples are shown in FIGS. 36 to 38. In thefigure, the portions corresponding to the components illustrated inFIGS. 33 to 35 are denoted by the same reference symbols and duplicateexplanations are omitted. At first, FIG. 36 shows an embodiment in whichthe columnar heat sinks 3 are arranged at different pitches in twostacked organic substrates 1.

On the other hand, FIG. 37 shows an embodiment in which only one of twostacked organic substrates 1 is provided with the columnar heat sinks 3,while the other is a heat-resistant insulating substrate having nocolumnar heat sink.

FIG. 38 shows a heat dissipation substrate in which a plurality oforganic substrates 1 having the columnar heat sinks 3 along with themetal layers 31, 32 on both sides thereof are stacked, and an organicsubstrate 1 having no columnar heat sink 3 is further stacked thereon.

The heat dissipation substrate according to the present invention may beused exclusively as a heat dissipation means or may be used as a circuitsubstrate such as a mother board, a submount board or the like.Referring to FIGS. 39 and 40, a given number (two in the figure) oforganic substrates 1 having the metal layers 31, 32 on both sidesthereof are stacked, and areas A1, A2 for mounting an electroniccomponent are defined in the bonded organic substrates 1, whereinthrough electrodes 2 to be exposed within the areas A1, A2 are providedto pass through the two organic substrates 1. The through electrode 2has a bump on at least one end thereof. The areas A1, A2 and the throughelectrodes 2 can be designed depending on the type of an electroniccomponent to be mounted.

FIGS. 41 and 42 show still another embodiment. Referring first to FIG.41, the substrate 1 is a conductive substrate, and the columnar heatsinks 3 are electrically insulated from the conductive substrate 1 by anorganic or inorganic insulating film 35 formed on an inner wall surfaceof the via 30 and one surface (lower surface) of the conductivesubstrate. The conductive substrate 1 may be a metal plate or an Sisubstrate.

Referring next to FIG. 42, the through electrodes 2 are provided inaddition to the columnar heat sinks 3. The through electrodes 2 areelectrically insulated from the conductive substrate 1 by the insulatingfilm 35.

As described above, the electronic device according to the presentinvention may be almost any electrical product based on the technologyof the electronics and its specific examples include a vehicle-mountedelectronic device. Examples of the vehicle-mounted electronic deviceinclude a motor drive inverter to be mounted on a hybrid vehicle or anelectric vehicle, a large-scale integration device (LSI) for LED lampcontrol and so on. Their specific examples will be described below.

FIG. 43 is a circuit diagram of a motor driver unit including a motordrive inverter. Referring to FIG. 43, the motor driver unit comprises aDC power supply 710, an inverter 730 and a controller 750 and isdesigned to drive a motor (or generator) 770 being a three-phase ACrotating electrical machine. The DC power supply 710 comprises, forexample, a secondary cell such as a nickel-metal hydride cell or alithium-ion cell, a capacitor, a condenser or a fuel cell.

The inverter 730 comprises a U-phase arm 73U, a V-phase, arm 73V and aW-phase arm 73W. The U-phase arm 73U comprises switching elements Q1, Q2connected in series, the V-phase arm 73V comprises switching elementsQ3, Q4 connected in series and the W-phase arm 73W comprises switchingelements Q5, Q6 connected in series. Furthermore, diodes D1 to D6 forpassing a current from the side of an emitter to the side of a collectorare connected between the collector and the emitter of the switchingelements Q1 to Q6, respectively.

At a midpoint, each phase arm is connected to a phase terminal of eachphase coil U, V, W of the motor 770. That is, the motor 770 isconstructed by commonly connecting one ends of U, V, W-phase three coilsto its neutral point, while the other end of the U-phase coil isconnected to a midpoint between the switching elements Q1, Q2, the otherend of the V-phase coil is connected to a midpoint between the switchingelements Q3, Q4 and the other end of the W-phase coil is connected to amidpoint between the switching elements Q5, Q6.

The inverter 730 converts a direct current voltage supplied from the DCpower supply 710 to an alternating current voltage based on a signal S1from the controller 750 and drives the motor 770 with the alternatingcurrent voltage. Thus, the motor 770 can be driven to generate a torquein accordance with a torque command value.

FIG. 44 is a drawing showing a mounted state of the switching elementbeing a component of the inverter of the motor driver unit shown in FIG.43. The inverter 730 is mounted on one side of a heat dissipationsubstrate 1 according to the present invention. The U-phase arm 73U ofthe inverter 730 comprises the switching elements Q1, Q2, a P-electrodelayer 63, an intermediate electrode layer 62 and an N-electrode layer61. Since the V-phase arm 73V and the W-phase arm 73W have a similarstructure, the following description will be made mainly for the U-phasearm 73U.

The U-phase arm 73U comprises the switching elements Q1, Q2, theP-electrode layer 63, the intermediate electrode layer 62 and theN-electrode layer 61 and is mounted on one side of the heat dissipationsubstrate 1 according to the present invention.

The P-electrode layer 63, the intermediate electrode layer 62 and theN-electrode layer 61 are all formed on the heat dissipation substrate 1by patterning. One end of the P-electrode layer 63 is connected to abusbar forming a power-supply line LN1. One end of the N-electrode layer61 is connected to a busbar forming a ground line LN2. The intermediateelectrode layer 62 corresponds to the midpoint of the U-phase arm 73U inFIG. 43. Although not illustrated, the busbars are also disposed on oneside of the heat dissipation substrate 1.

The switching element Q1 is adhered to the intermediate electrode layer62 to bring the collector into conduction with the intermediateelectrode layer 62. The emitter of the switching element Q1 is connectedto the P-electrode layer 63 through a wire WL1.

The switching element Q2 is adhered to the N-electrode layer 61 to bringthe collector into conduction with the N-electrode layer 61. The emitterof the switching element Q2 is connected to the intermediate electrodelayer 62 through a wire WL1.

The heat dissipation substrate 1 is of the type having an insulatinglayer on one side (upper side) where the switching elements Q1, Q2, theP-electrode layer 63, the intermediate electrode layer 62 and theN-electrode layer 61 are to be mounted, while the metal layer 31 on thelower side is put on a heat dissipation block 50 through a siliconegrease.

The heat dissipation block 50 has a plurality of grooves 501. When awater cooling system is used as a cooling system of the inverter 730,cooling water supplied from an external radiator (not shown) flows downthe plurality of grooves 501 of the heat dissipation block 50 in adirection perpendicular to the plane of paper, thereby cooling theswitching elements Q1, Q2 through the heat dissipation substrate 1. Theswitching elements Q3 to Q6 have the same cooling system.

In a hybrid vehicle or an electric vehicle, since the motor 770 isdriven by converting a direct current voltage supplied from the DC powersupply 710 to an alternating current voltage using the inverter 730, alarge current flows through the switching elements Q1 to Q6 and thebusbars constituting the inverter 730. Thus, the question of how to coolsuch a heat-generating part becomes a major issue.

In addition to the electrical insulation to the switching elements Q1,Q2, the P-electrode layer 63, the intermediate electrode layer 62, theN-electrode layer 61 and so on, the heat dissipation substrate 1according to the present invention has a heat dissipation pathway formedby the columnar heat sinks 3, whereby heat of the switching elements Q1to Q6 and the busbars constituting the inverter 730 can be efficientlytransferred to the heat dissipation block 50, contributing to cooling ofthe switching elements Q1 to Q6, the busbars and so on.

Next will be described an embodiment in which the heat dissipationsubstrate according to the present invention is used for a personalcomputer, a mobile phone, a digital appliance or the like by referringto FIGS. 45 and 46. Referring first to FIG. 45, an electronic component6 is mounted on one side of the heat dissipation substrate 1 accordingto the present invention.

The electronic component 6 is constructed by stacking and bonding alogic element 6A such as an LSI and a memory element 6C such as a DRAMthrough an interposer 6B. Electronic devices of this type can be used asa basic element of an information processing system. More specifically,they can be used as a component of an image processing system in apersonal digital assistant, a mobile phone, a digital appliance, aserver or the like. There are other uses, including an image sensormodule.

The logic element 6A is in the form of a chip containing a semiconductorlogic circuit such as an LSI. The interposer 6B has a decouplingcapacitor and a through electrode, wherein one end of the throughelectrode is connected to the logic element 6A, while the other end ofthe through electrode is connected to the memory element 6C. This makesit possible to obtain an electronic component having a three-dimensionalstructure based on the TSV technology. The interposer 6B can be obtainedby forming the through electrode in an Si substrate, a resin substrateor a ceramic substrate. However, the layer number and type of theelements constituting the electronic component 6, the arrangement oftheir electrodes and so on can vary widely depending on the usedelectronic component 6, and FIG. 45 merely shows one conceptual exampleof the three-dimensional multilayer structure.

In this structure, since the metal layers 31, 32 to be used as a heatdissipation pathway are provided at a middle portion of the stackedorganic substrates 101, 102, there is created a three-dimensional heatdissipation structure in which in addition to heat dissipation throughthe columnar heat sinks 3, heat transferred from the columnar heat sinks3 can be dispersed in a planar direction at the middle portion of thesubstrates 1. Thus, heat can be prevented from being accumulated withinthe substrates 1, thereby suppressing temperature rise of the electroniccomponent 6 to be mounted on the substrates 1.

Although not illustrated, the logic element 6A, the interposer 6B andthe memory element 6C can also contain similar columnar heat sinks,wherein heat dissipation effect can be further improved by connectingthe columnar heat sinks continuously and thermally coupling them to thecolumnar heat sinks 3 of the mother board 1.

Referring next to FIG. 46, there is illustrated an embodiment in which asubmount board 1B containing the electronic component 6 is mounted onone side of a mother board 1A. The mother board 1A is similar to thatshown in FIG. 19 and has a structure in which two organic substrates101A, 102A having metal layers 31A, 32A on two sides thereof are stackedwith the metal layers 31A, 32A located at an interface.

In the submount board 1B, there are disposed not only columnar heatsinks 3B but also through electrodes 2B. The submount board 1B has acavity 11 at one side thereof, and the columnar heat sinks 3Belectrically insulated by an insulating layer 35B are provided in athick portion around the cavity 11. One end of the columnar heat sink 3Bis connected to a metal layer 31B. The through electrodes 2B areprovided at the bottom of the cavity 11 and electrically insulated bythe insulating layer 35B.

The electronic component 6 is housed in the cavity 11, and electrodes(bumps) provided on the lower surface of the logic element 6A areconnected to one ends of the through electrodes 2B.

In the case of FIGS. 45 and 46, since the columnar heat sinks 3A, 3B areprovided in the mother board 1A and the submount board 1B, heatgenerated by the operation of the electronic component 6 can betransferred from the submount board 1B to the mother board 1A throughthe columnar heat sinks 3A, 3B and dissipated to the outside.Accordingly, abnormal heat generation due to heat accumulation can beprevented to avoid a variation in electrical characteristics of theelectronic component 6 due to the heat generation.

The submount board 1B has the cavity 11 at one side thereof and containstherein the electronic component 6. Many columnar heat sinks 3B eachpassing through the submount board 1B in the thickness direction arearranged around the cavity 11 at a small distance from each other. Thismeans that a heat dissipation pathway is formed by the columnar heatsinks 3B to three-dimensionally surround the electronic component 6housed in the cavity 11, so that heat generated at the electroniccomponent 6 can be, collected three-dimensionally and dissipatedefficiently.

While the present invention has been particularly shown and describedwith respect to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and detail may bemade therein without departing from the spirit, scope and teaching ofthe invention.

What is claimed is:
 1. A substrate for an electronic device, thesubstrate having a first side and a second side opposite to the firstside, the substrate comprising: a first via passing through from thefirst side to the second side of the substrate; a through electrodeformed in the first via; a second via passing through from the firstside to the second side of the substrate; a heat sink formed in thesecond via; a recess formed on the first side, wherein the recessincludes a bottom wall and side walls, wherein a top surface of thethrough electrode reaches to the bottom wall of the recess, wherein therecess is capable of mounting an electronic component thereon, and areflection film provided on the side walls of the recess, wherein thereflection film is one of an Al film, an Ag film or a Cr film; whereinthe through electrode and the heat sink have a nanocomposite structureconsisting of a nm-sized carbon nanotube and a metal/alloy componenthaving a nanocomposite crystal structure, the metal/alloy componentincluding Cu, wherein the through electrode and the heat sink have acompact structure free from any cavity, void or hollow and kept in closecontact with a side wall surface of each of the first via and the secondvia, wherein the through electrode and the heat sink are made by castinga liquid state of a mixture consisting of the metal/alloy component andthe nm-sized carbon nanotube into the first via and the second via,followed by solidifying the mixture to form the through electrode andthe heat sink.
 2. The substrate of claim 1, including at least one of aninorganic substrate, an organic substrate and a semiconductor substrate.3. The substrate of claim 2, wherein the through electrode iselectrically insulated from the substrate by an electrical insulatingfilm or electrical insulating layer.
 4. The substrate of claim 1,wherein the heat sink is electrically insulated from the substrate by anelectrical insulating film or electrical insulating layer.
 5. Thesubstrate for the electronic device according to claim 1, wherein theelectronic component is mounted on the bottom wall of the recess of thesubstrate.